Electric cartridge fuse

ABSTRACT

An electric cartridge fuse includes a tubular main casing and a tubular sub-casing inside of the main casing. The latter is closed at least one one side thereby by an additional cover means resting against an axially outer edge of the sub-casing and held in position by a radially outwardly projecting bulge formed in the fusible element of the fuse and engaging the cover means adjacent the center thereof. Further disclosed are other applications of the fusible element bulge concept for positioning partitions in electric cartridge fuses.

United States Patent Belcher 154] ELECTRIC CARTRIDGE FUSE [72] Inventor:Richard A. Belcher, Hampton Falls,

Assignee: The Chase-Shawmut Newburyport, Mass.

Filed: May 13, 1971 Appl. No.2 142,877

[ Company,

' I References Cited UNITED sTATEs PATENTS 12/1966 Kozocka; ..337/16611/1910 Leueenetal. ..337/231 51 Oct. 24, 1972 3,291,942 12/1966 Kozocka..337/276 X 2,787,684 4/1957 Laing ..337/292 X 1,425,692 8/ 1922 Procteret al. ..337/23l X 3,483,501 12/1969 Kozocka ..337/166 1,103,987 7/1914Murray ..337/248 Primary Examiner-Roy N. Envall, Jr. Attorney-ErwinSalzer [57] ABSTRACT An electric cartridge fuse includes a tubular maincasing and a tubular sub-casing inside of the main casing. The latter isclosed at least one one side thereby by an additional cover meansresting against an axially outer edge .of the sub-casing and held inposition by a radially outwardly projecting bulge formed in the fusibleelement vof the fuse and engaging the cover means adjacent the centerthereof. Further disclosed are other applications of the fusible elementbulge concept for positioning partitions in electric cartridge fuses.

9 Claims, 9 Drawing Figures PATENTED BI 24 7 3.701.069

sum 1 or 2 all I! i l/7. I

mvemoa: RICHARD A. BELCHER BY g ATTY.

PATENTEDHN24 Ian 3.701.069

II'IIII I 'IIIIIII III/IA J "II/III/IIII/III/I/ I INVENTOR: RICHARD A.BELCHER BY MAM M ATTY.

ELECTRIC CARTRIDGE FUSE BACKGROUND OF THE INVENTION The design ofcartridge fuses often calls for the provision of a sub-casing arrangedinside of the main or principal casing of the fuse housing portion ofthe fusible element means of the fuse and keeping the pulverulentarc-quenching filler embedding other portions of the fusible elementmeans away from the particular portion thereof which is housed in thesub-housing.

One structure of the aforementioned character is disclosed and claimedin U.S. Pat. No. 3,294,937 to Frederick J. Kozacka, Dec. 27, 1966 forTIME LAG DUAL ELEMENT FUSE HAVING MEANS FOR PRECLUDING ARC INITIATIONADJACENT TER- MINALS. Another structure of the aforementioned characteris disclosed and claimed in US. Pat. No. 3,483,501 to Frederick J.Kozacka, Dec. 9,1969 for ELECTRIC CARTRIDGE FUSE.

The structure shown in the first mentioned patent includes a sub-casingformed by a length of tubular insulating material which is closed onboth sides by additional cover means. The structure shown in the lastmentioned patent includes a sub-casing formed by a length of tubularinsulating material which is squashed and flattened on one side andclosed by a staple on the side where squashed and flattened. The firstmentioned alternative is more desirable as it does not affect themechanical integrity of the sub-casing, is not limited to casingmaterials capable of being squashed and flattened, and does not reducethe space availableinside of the sub-casing as in case that one side ofthe sub-casing is closed by squashing, flattening and stapeling of theflattened end of the sub-casing. The squashed, flattened and stapledvariety of sub-casing is, however, much less expensive to manufacturethan that shown in US. Pat. No. 3,294,937.

It is, therefore, the principal object of the invention to providecartridge fuses including sub-casings which fuses have all theadvantages of prior art fuses whose sub-casings are covered byadditional cover means, but whose cost of manufacture is much less thanthose of prior art fuses whose sub-casings are covered by additionalcover means.

SUMMARY OF THE INVENTION An electric fuse embodying this inventionincludes a tubular main casing and a pair of terminal elements arrangedat the ends of said main casing and closing the same. Fusible elementmeans inside the main casing conductively interconnect said pair ofterminal elements. Said fusible element means include a major faultcurrent interrupting portion in ribbon form and an overload currentinterrupting portion. A body of pulverulent arc-quenching filler iscontained inside the main casing, and the major fault currentinterrupting portion of the fusible element means is embedded in thebody of arc-quenching filler. A tubular sub-casing inside of the maincasing houses the overload current interrupting portion of the fusibleelement means and separates the latter from the pulverulentarc-quenching filler. A perforated cover means is arranged at least atone of the end surfaces of the sub-casing, closing the sub-casing andallowing passage of the fusible element means. The closing means ismaintained in position by fastener means. The latter include a radiallyoutwardly projecting mound-like bulge formed in said fusible elementmeans andforrning an abutment engaging said cover means. The bulge isbounded by a closed curve situated within the surface or plane definedby said fusible element means. This means that the formation of any gapor gaps between the mound-like bulge and the fault current interruptingportion of the fusible element is avoided, and/or that the mound-likebulge is unsevered at any point thereof from the fault currentinten'upting portion of the fusible element.

The aforementionedfastener means are not limited to cartridge fusesincluding casings and sub-casings, but may be applied whereever it isdesired to sub divide the casings of cartridge fuses by means ofpartitions into separate chambers.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal section of acartridge fuse embodying this invention taken substantially along I-I ofFIG. 3;

FIG. 2 is an end view of the structure of FIG. 1;

FIG. 3 is a longitudinal section of the same fuse as shown in FIG. 1taken along III-III of FIG. 1;

FIG. 4 is a longitudinal section of another cartridge fuse embodyingthis invention;

FIG. 5 is an isometric view of a detail of the structures of FIGS. l-4;

FIG. 6 is a longitudinal section on a larger scale than FIGS. 1-4 of thedetail of the structures of FIGS. 1-4 shown in FIG. 5;

FIG. 7 is a longitudinal section of another fuse embodying thisinvention;

FIG. 8 is a longitudinal section of still another fuse embodying thisinvention; and

FIG. 9 is a longitudinal section of a fuse similar to that shown inFIGS. I-3 and embodying this invention.

DESCRIPTION OF PREFERRED EMBODIMENT Reference character 1 has beenapplied to indicate a tubular main casing of electric insulatingmaterial closed on the ends thereof by a pair of terminal elements orterminal caps 2 mounted on the outer surface of casing 1. Caps 2 areconductively connected by fusible element means. A tubular sub-casing 3is arranged inside of main casing 1 in coaxial relation to the latter.The fusible element means are formed by a ribbon of silver or of copperhaving serially related points of reduced cross-sectional area formed bycircular perforations. The portion of the fusible element means insideof sub-casing 3 is provided with an overlay 4 of a metal capable ofsevering upon fusion thereof by a metallurgical reaction the base metalsilver or copper, respectively upon which the overlay 4 is deposited.The portions 5a of the fusible element means outside of sub-casing 3 aremajor fault current interrupting means and the portion 5b withinsub-housing 3 supporting overlay 4 are a means for interrupting overloadcurrents. The main casing 1 contains a body of pulverulent arc-quenchingfiller 6, e.g., quartz sand. Sub-casing 3 keeps the arc-quenching filler6 away from the overload interrupting portion 5b of the fusible elementmeans. The sub-casing 3 is closed on both its ends by disc-shaped covermeans 7 of electric insulating material, e.g., vulcanized fiber. Eachdisc 7 engages and abuts against the circular edge of sub-casing 3 imaof the fusible element means immediately adjacent cover means 7 areprovided with a radially outwardly projecting bulge 5c formed in thefusible element means and forming abutments engaging cover means 7adjacent the centers thereof and maintaining cover means 7 in firmengagement with the circular edges of sub-casing 3. As is apparent fromFIGS. 5 and 6 the bulge 5c is bounded by a closed, substantiallyeggshaped curve which is situated within the surface or plane defined bythe fault current interrupting portion 5a of the fusible element means.

Upon occurrence of a major fault the portions 50 of fusible elementmeans fuse and form series breaks, resulting in a sufficiently high arevoltage to cause a current-limiting interruption of the fault currents.Upon occurrence of overloads of inadmissible duration overlay 4 meltsand causes formation of a break inside of sub-housing 3. The length ofthis break increases by burnback resulting in an arc voltage which issufficiently high at the end of a few half cycles to result in thecessation of current flow.

The same reference characters as in FIGS. 1 and 3 with a prime addedhave been applied in FIG. 4 to indicate like parts.

Main casing 1 closed by terminal caps 2' houses coaxial sub-casing 3'. Acup 8 of brass or like metal closes the left side of sub-housing 3, anda disc 7 of insulating material closes the right side of sub-housing 3'.Cup 8 houses plunger 9 biased from right to left by helical spring 10.Ribbon fuse link sections 5a connect terminal caps 2' conductively withcup 8 and plunger 9, respectively. Reference character 11 has beenapplied to indicate a solder joint conductively connecting the axiallyinner end of left ribbon link section 5a to cup 8. Reference character12 has been applied to indicate solder joints conductivelyinterconnecting cup 8 and plunger 9 (which are relatively movablecontacts) and conductively connecting right fuse link section 5a andplunger 9. The right fuse link section 5a is provided with bulge 5cabutting against the center region of cover disc 7 and maintaining thelatter in firm engagement with the right hand edge of sub-casing 3.

Bulges 5c and 5c, respectively, are formed by the displacement of metalout of the general plane of the ribbon fuse links 5 and 5a respectively.The formation of bulges 5c and 50 does not involve the removal of metaland does not affect the current rating of the fuse structures.

The fuse shown in FIG. 4 operates in the same way as that shown in FIGS.1 and 2 when subjected to major fault currents. Upon occurrence ofprotracted overload currents solder joints 12 melt and plunger 9 is thenfree to move and moves under the action of spring from right to left. Asa result, an arc gap is formed between plunger 9 and the axially innerend of right fuse link portion 5a. As shown in FIGS. 5 and 6 bulge 5c isnot symmetrical, its slope adjacent cover disc 7 being steeper than itsslope at the side remote from cover disc 7, where no abutment functionis required.

Referring now to FIG. 7, the tubular casing 1" of electric insulatingmaterial, e.g., fiber, is closed on the ends thereof by terminal caps2". The latter are conductively interconnected by ribbon fuse link 5".Casing 1" is subdivided by a partition 13 into a left chamber 14 and aright chamber 15. The diameter of partition 13 is substantially the sameas the inner diameter of casing 1". Partition 13 has a slit for thepassage of fusible element 5" and the latter is provided with two radialbulges each to one side of partition 13. The

bulges 5c" are of the same nature as the bulges 5c shown in FIGS. 5 and6 and described in their context. Chamber 15 is filled with apulverulent arc-quenching filler 16, and chamber 14 may be filled withpulverulent filler other than filler 16, or does not contain any filler.

The structure of FIG. 8 is substantially the same as that of FIG. 7,except that the former is provided with two partitions 13, each clampedbetween a pair of bulges or mounds 50" formed by ribbon fuse link 5".Partitions 13 form a center chamber 17 which does not contain anypulverulent arc-quenching filler, and a pair of axially outer chambers18 containing the pulverulent arc-quenching filler 19. Referencecharacter 4" has been applied to indicate a link-severing overlay of alow fusing point metal, e.g., tin, placed on ribbon link 5" of copper orsilver.

The modification of the structure of FIGS. 1-3 shown in FIG. 9 includescasing l, sub-casing 3, fusible element 5a,5b,5a, pulverulentarc-quenching filler 6, a pair of cover plates 7 for sub-casing 3, and alow fusing point link-severing overlay 4 on portion 5b of the fusibleelement or fuse link. The left cover plate 7 for subcasing 3 is arrangedbetween two mounds or bulges 5c of fuse link 5a,5b,5a and the rightcover plate 7 of subcasing 3 is clamped by a mound or bulge 5c of thefuse link 5a,5b,5a against the right rim or circular edge of sub-casing3.

In terms of performance the structure of FIG. 9 does not differ fromthat of FIGS. 1-3, however, the structure of FIG. 9 may be assembled ina way different from the structure of FIGS. 1-3, which mode of assemblyis particularly desirable in some instances.

When assembling the structure of FIG. 9 first the bulge 5c situated tothe left of left cover plate 7 is formed, thereafter the fuse link isthreaded through the slit in the aforementioned cover plate intended forthe passage of the fuse link, thereafter the bulge 50 to the right ofthe aforementioned cover plate 7 is formed, thereafter the fuse link isthreaded through sub-casing 3 until the left edge or rim thereof abutsagainst left cover plate 7, thereafter the fuse link is threaded throughthe slit in right cover plate 7 intended for the passage thereof untilit is engaged by the right rim or edge of sub-casing 3, and finally theright bulge or mound 5c is formed in the fuse link 5a,5b,5a.

The formation of mounds or bulges 5c,5c and 5c" is effected by means ofa small tool or press, appropriate for the purpose in hand.

I claim as my invention:

1. An electric cartridge fuse including a. a tubular main casing;

b. a pair of terminal elements arranged at the ends of said main casingand closing said main casing;

c. fusible element means inside said main casing conductivelyinterconnecting said pair of terminal elements; said fusible elementmeans including a major fault current interrupting portion in ribbonform and an overload current interrupting portion;

d. a body of pulverulent arc-quenching filler inside said main casingembedding said major fault current interrupting portion of said fusibleelement means;

e. a tubular sub-casing inside said main casing housing said overloadcurrent interrupting portion of said fusible element means andseparating said overload current interrupting portion of said fusibleelement means from said arc quenching filler;

f. perforated cover means at least at one of the end surfaces of saidsub-casing closing said sub-casing and allowing passage of said faultcurrent interrupting portion of said fusible element means; and

g. fastener means abutting against said cover means for maintaining saidcover means in position, said fastener means including a radiallyoutwardly projecting mound-like bulge formed in said fault currentinterrupting portion of said fusible element means by transverselydisplaced metal thereof, said transversely displaced metal forming saidmound-like bulge being unsevered at any point or points thereof from thefault current interrupting portion of said fusible element, thusavoiding gap formation between said mound-like bulge and said faultcurrent interrupting portion of said fusible element, and saidmound-like bulge being bounded by a closed curve situated within theplane defined by said fault current interrupting portion of said fusibleelement means.

2. An electric cartridge fuse as specified in claim 1 wherein a. saidsub-casing houses a pair of separable, springbiased, normallysolder-means-restrained contacts, one of said pair of contacts closingone of the end surfaces of said sub-casing; and wherein b. saidperforated cover means closes the other of the end surfaces of saidsub-casing and abuts on one side thereof against the edge formed by theend of said-sub-housing remote from said one of said pair of contactsand abuts on the other side thereof against an external moundlike bulgeof said fault current interrupting portion in ribbon form of saidfusible element means.

3. An electric cartridge fuse as specified in claim 1 wherein saidperforated cover means is formed by a circular disc of electricinsulating material having a straight radially extending slot for thepassage of said fault current interrupting portion of said fusibleelement means, and wherein said outwardly projecting mound-like bulgeengages said disc at a point immediately adjacent to the center of saidslot.

4. An electric cartridge fuse as specified in claim 3 wherein the slopeof said mound-like bulge is steeper at the side of said bulge adjacentsaid disc than at the side of said mound-like bulge remote from saiddisc.

5. In an electric cartridge fuse the combination of a. a tubular casingof electric insulating material;

b. a fusible element in ribbon form arranged inside said casing;

c. a plate of insulating material arranged at right angles to saidcasing and having a slit therein for the passage of said fusibleelement, said fusible element projecting from one side of said platethrough said slit to the other side of said plate; and

d. means for positioning said plate relative to said in "i fnilfiillbiflltifiilfieil ufniifii oililiity transversely displaced fusibleelement metal unsevered at any point or points thereof from said fusibleelement and thus avoiding gap formation between said mound-shapedabutment and said fusible element, and said mound-shaped abutment beingbounded by a closed curve situated within the plane defined by saidfusible element.

6. An electric fuse as specified in claim 5 wherein said plate separatesspaces containing different media.

7. An electric cartridge fuse as specified in claim 5 wherein a. saidtubular casing is provided with terminal caps on the ends thereof;wherein b. said terminal caps are conductively interconnected by saidfusible element; wherein c. said plate has the same diameter as theinner wherein a. said tubular casing is arranged inside of anothertubular casing of electric insulating material, said another casinghaving a larger inner diameter than the outer diameter of said casing;wherein b. said another casing is provided with terminal caps on theends thereof and said terminal caps are conductively interconnected bysaid fusible element; and wherein c. said plate is positioned relativeto said fusible element by abutting engagement on one side thereof byone of the rims formed by one of the ends of said casing and is furtherpositioned relative to said fusible element by engagement on the otherside thereof by said substantially mound-shaped abutment.

9. An electric cartridge fuse as specified in claim 8 wherein a. saidcasing is closed on each of both ends thereof by one of a pair of platesof insulating material each having substantially the same diameter asthe diameter of said casing; wherein b. one of said pair of plates ispositioned relative to said fusible element by a pair of substantiallymound-shaped abutments formed by transversely displaced fusible elementmetal each being bounded by a closed curve situated within the surfacedefined by said fusible element; and wherein c. the other of said pairof plates is in abutting engagement on one side thereof with one of therims formed by one of the ends of said casing, and is engaged on theother side thereof by a substantially mound-shaped abutment formed bytransversely displaced fusible element metal and being bounded by aclosed curve situated within the surface defined by said fusibleelement.

1. An electric cartridge fuse including a. a tubular main casing; b. apair of terminal elements arranged at the ends of said main casing andclosing said main casing; c. fusible element means inside said maincasing conductively interconnecting said pair of terminal elements; saidfusible element means including a major fault current interruptingportion in ribbon form and an overload current interrupting portion; d.a body of pulverulent arc-quenching filler inside said main casingembedding said major fault current interrupting portion of said fusibleelement means; e. a tubular sub-casing inside said main casing housingsaid overload current interrupting portion of said fusible element meansand separating said overload current interrupting portion of saidfusible element means from said arc-quenching filler; f. perforatedcover means at least at one of the end surfaces of said sub-casingclosing said sub-casing and allowing passage of said fault currentinterrupting portion of said fusible element means; and g. fastenermeans abutting against said cover means for maintaining said cover meansin position, said fastener means including a radially outwardlyprojecting mound-like bulge formed in said fault current interruptingportion of said fusible element means by transversely displaced metalthereof, said transversely displaced metal forming said mound-like bulgebeing unsevered at any point or points thereof from the fault currentinterrupting portIon of said fusible element, thus avoiding gapformation between said mound-like bulge and said fault currentinterrupting portion of said fusible element, and said mound-like bulgebeing bounded by a closed curve situated within the plane defined bysaid fault current interrupting portion of said fusible element means.2. An electric cartridge fuse as specified in claim 1 wherein a. saidsub-casing houses a pair of separable, spring-biased, normallysolder-means-restrained contacts, one of said pair of contacts closingone of the end surfaces of said sub-casing; and wherein b. saidperforated cover means closes the other of the end surfaces of saidsub-casing and abuts on one side thereof against the edge formed by theend of said sub-housing remote from said one of said pair of contactsand abuts on the other side thereof against an external mound-like bulgeof said fault current interrupting portion in ribbon form of saidfusible element means.
 3. An electric cartridge fuse as specified inclaim 1 wherein said perforated cover means is formed by a circular discof electric insulating material having a straight radially extendingslot for the passage of said fault current interrupting portion of saidfusible element means, and wherein said outwardly projecting mound-likebulge engages said disc at a point immediately adjacent to the center ofsaid slot.
 4. An electric cartridge fuse as specified in claim 3 whereinthe slope of said mound-like bulge is steeper at the side of said bulgeadjacent said disc than at the side of said mound-like bulge remote fromsaid disc.
 5. In an electric cartridge fuse the combination of a. atubular casing of electric insulating material; b. a fusible element inribbon form arranged inside said casing; c. a plate of insulatingmaterial arranged at right angles to said casing and having a slittherein for the passage of said fusible element, said fusible elementprojecting from one side of said plate through said slit to the otherside of said plate; and d. means for positioning said plate relative tosaid fusible element, said positioning means including a substantiallymound-shaped abutment formed by transversely displaced fusible elementmetal unsevered at any point or points thereof from said fusible elementand thus avoiding gap formation between said mound-shaped abutment andsaid fusible element, and said mound-shaped abutment being bounded by aclosed curve situated within the plane defined by said fusible element.6. An electric fuse as specified in claim 5 wherein said plate separatesspaces containing different media.
 7. An electric cartridge fuse asspecified in claim 5 wherein a. said tubular casing is provided withterminal caps on the ends thereof; wherein b. said terminal caps areconductively interconnected by said fusible element; wherein c. saidplate has the same diameter as the inner diameter of said casing andsubdivides said casing into a pair of compartments; and wherein d. saidmeans for positioning said plate relative to said fusible elementinclude a pair of substantially mound-shaped abutments formed bytransversely displaced fusible element metal and arranged to oppositesides of said plate, each of said mound-shaped abutments being boundedby a closed curve situated within the surface defined by said fusibleelement.
 8. An electric cartridge fuse as specified in claim 5 whereina. said tubular casing is arranged inside of another tubular casing ofelectric insulating material, said another casing having a larger innerdiameter than the outer diameter of said casing; wherein b. said anothercasing is provided with terminal caps on the ends thereof and saidterminal caps are conductively interconnected by said fusible element;and wherein c. said plate is positioned relative to said fusible elementby abutting engagement on one side thereof by one of the rims formed byone of the ends of said casing and is further positioned relative toSaid fusible element by engagement on the other side thereof by saidsubstantially mound-shaped abutment.
 9. An electric cartridge fuse asspecified in claim 8 wherein a. said casing is closed on each of bothends thereof by one of a pair of plates of insulating material eachhaving substantially the same diameter as the diameter of said casing;wherein b. one of said pair of plates is positioned relative to saidfusible element by a pair of substantially mound-shaped abutments formedby transversely displaced fusible element metal each being bounded by aclosed curve situated within the surface defined by said fusibleelement; and wherein c. the other of said pair of plates is in abuttingengagement on one side thereof with one of the rims formed by one of theends of said casing, and is engaged on the other side thereof by asubstantially mound-shaped abutment formed by transversely displacedfusible element metal and being bounded by a closed curve situatedwithin the surface defined by said fusible element.